Rf meter reading system

ABSTRACT

The automatic meter reading (AMR) systems and methods of the present invention facilitate meter reading utilizing one-way and two-way communication with utility meter endpoint devices while at the same time providing an operating regime that conserves energy for long battery life and utilizes the available airwaves for AMR communications efficiently. Embodiments of the invention are applicable in AMR systems employing handheld and/or vehicle-based mobile readers, fixed readers, and combinations thereof. Moreover, embodiments of the invention facilitate smooth transition from mobile AMR systems to fixed systems, and provide for automatic AMR system performance monitoring and automatic adaptability to maintain or improve performance.

PRIORITY CLAIM

This application is a continuation of U.S. patent application Ser. No.11/991,677, filed Sep. 11, 2006, to issue Mar. 5, 2013 as U.S. Pat. No.8,390,472, which is a U.S. national phase application of PCTInternational Application No. PCT/US2006/035508, also filed Sep. 11,2006, which claims priority to U.S. Ser. No. 11/222,657 filed Sep. 9,2005, now U.S. Pat. No. 7,535,378 issued May 19, 2009, all entitled “RFMETER READING SYSTEM”, and all of which are hereby incorporated hereinby reference in their entireties for all purposes. Any disclaimer thatmay have occurred during prosecution of the above-referencedapplication(s) is hereby expressly rescinded.

FIELD OF THE INVENTION

The present invention is directed to automatic utility meter readingsystems and, more specifically, is directed to an automatic utilitymeter reading system wherein the system synchronizes the reader to theendpoints and provides multipoint two-way meter reading.

BACKGROUND OF THE INVENTION

In radio-based automatic meter reading (AMR) systems, many utility meterendpoints need to be read by each reader. This type of communicationsarrangement is known as a point-multipoint system. One challenge in thedesign and deployment of such systems is ensuring that each endpointdevice can be read reliably and as often as needed to meet the utility'sbilling cycle and measurement granularity requirements. Some utilitiesmay wish to obtain hourly reads, for example, to monitor usage patterns.Certain utility providers may need to obtain consumption data from alarge numbers of meters within a certain time window to determine itstotal “day take” of each most recent 24-hour period, for example.

Traditionally, AMR systems have utilized one-way endpoint devices thatperiodically transmit their consumption and related information as a“bubble-up” event. This type of transmission is known as a one-waysystem because the endpoint sends only outbound communications and doesnot receive any commands or acknowledgements from the reader. Forordinary remote reads, the endpoint has no way of knowing if itstransmission has been received or if it needs to re-transmit a failedcommunication. Likewise, in systems wherein a reader is onlyoccasionally within communication range of an endpoint, one-wayendpoints have no way of knowing when a reader is present. One-waysystems are designed such that endpoint devices transmit their messagesfrom once every several seconds to once per minute. Because messages aretransmitted so frequently, their length must be kept short to conserveenergy in battery-powered endpoints. In addition, messages arepreferably kept short to reduce the likelihood that messages willcollide. This latter challenge exists regardless of whether endpointsare battery or externally powered.

Other known AMR systems utilize 1.5-way or two-way endpoint devices.One-and-one-half-way and two-way endpoints operate in a listen mode formost of the time. Reads are accomplished by interrogating specificendpoint devices by the reader. Collisions are reduced because endpointswithin a reader's communication range can be interrogated one-at-a-time.In a 1.5-way system, an endpoint responds to a wakeup tone from a readerby transmitting its consumption and related information. In a two-waysystem, endpoint devices are responsive to various additional commandsfrom the reader that may specify what type of information an endpointshould transmit, and that may configure operating parameters of theendpoint. One drawback of these two-way systems is the need forendpoints to operate in a receive mode (either frequently orcontinuously) in order to detect an interrogation signal or othercommand from the reader.

Another drawback of interrogation-based 1.5-way or two-way AMR systemsis their incompatibility with the one-way systems described above, whichare widely deployed. A simple one-way endpoint cannot detect or respondto an interrogation signal. Also, in areas where there might be simpleone-way endpoints near interrogation mode endpoints, transmissions fromthe one-way endpoint would not be coordinated with those of theinterrogation mode endpoints, resulting in an increased likelihood ofmessage collisions. To date, no practical solution has been proposedthat takes advantage of the power savings, backwards compatibility, andthe other advantages of bubble-up systems, while enabling the moreadvanced functionality and remote configurability of interrogation modesystems.

Various AMR systems utilize hand-held readers and programming devices,vehicle-mounted readers, fixed location readers, and combinationsthereof. Endpoints and readers among these different systems arepreferably operated with different time periods between communicationattempts, and different transmission power levels. As the size of autility provider's customer base increases, the utility will tend tomigrate from utilizing handheld readers to vehicle-based readers, andeventually to fixed reader systems. One challenge associated with makingsuch a migration is the difficulty in re-configuring the AMR systemdevices to adjust their cooperating mode. Therefore, migration involvesa substantial investment, not only in infrastructure upgrades, but infield labor.

SUMMARY OF THE INVENTION

The needs described above are in large part met by the meter readingsystem and method of the present invention. The meter reading systemgenerally includes a reader and a utility meter endpoints. Anintermediary repeater may also be used. In one embodiment of theinvention, the endpoints bubble up to transmit an initial (short)message transmission of at least their identification. The endpoint thenturns off its transmitter to save on battery power, and enters a listenmode for any instructions from the reader, such as, for example, such asa request for additional information. If the endpoint receives theseinstructions during its listen period, the endpoint responds asinstructed. If the endpoint does not receive a response from the reader,the endpoint enters a sleep mode until its next transmit time to, onceagain, save batter power.

A method of this embodiment includes the steps of: (1) waking up each ofthe endpoints; (2) transmitting/bubbling up an initial message from eachof the endpoints; (3) listening with the endpoint for a response fromthe reader; (4) listening by the reader for the initial messagetransmission; (5) upon the reader receiving the initial messagetransmission, requesting additional information from the endpoint; (6)upon receiving the request for additional information, transmitting theadditional information requested from the endpoint; and (7) upon notreceiving the request for additional information, entering a sleep modewith said endpoint until a next pre-programmed initial messagetransmission time.

Another embodiment of the invention provides for the endpoint totransmit a standard consumption message (SCM) via AM communication.Immediately, upon transmitting the AM communication, the endpointtransfers into a two-way, FM receive/transmit mode. When the readerreceives the SCM, the reader requests additional information from theendpoint and the endpoint transmits that additional information via thetwo-way FM communication.

A method of one embodiment includes the steps of: (1) transmitting anSCM via AM transmission from the endpoint; (2) switching the endpointinto a two-way FM transmit/receive mode upon completing the AMtransmission; (3) receiving the SCM with the reader; and (4) requestingadditional information from the endpoint with the reader by two-way FMcommunication between the reader and endpoint.

In still another alternative embodiment of the present invention, theendpoint operates to save intervals of utility meter data. This intervaldata is capable of being transmitted by the endpoint in either AM or FM.In this instance, the reader, upon detecting the endpoint, transmits acommand to the endpoint to send a predetermined number of intervals overa predetermined communication channel or channels.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a radio-based automatic meter reading system thatutilizes the data communication protocol according aspects of thepresent invention.

FIG. 2 is a flow diagram illustrating an AMR system communicationsession between an endpoint and a reader according to one embodiment ofthe invention.

FIGS. 3A and 3B illustrate examples of messages that can be communicatedin one-way communications and two-way communications modes according tovarious embodiments.

FIG. 4 is a decision tree diagram illustrating examples of the responseby an endpoint to the initiation of two-way communications by a reader.

FIG. 5 is a block diagram illustrating a portion of the components of anAMR system reader according to one embodiment of the invention.

FIG. 6 is a timing diagram illustrating two-way communications between areader and a plurality of endpoints during four consecutive blocks oftime I-IV according to one example embodiment.

FIGS. 7A and 7B are flow diagrams illustrating an example communicationsequence involving a reader, an endpoint, and a repeater according toone aspect of the invention.

FIGS. 8A and 8B are diagrams illustrating examples of data structuresfor storing consumption values in endpoints according to one aspect ofthe invention.

FIG. 9 is a circuit diagram illustrating an example embodiment of aswitched capacitor arrangement for temporarily boosting the availablepower for powering the transmitter circuit during data transmissions.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The automatic meter reading (AMR) systems and methods of the presentinvention facilitate meter reading utilizing one-way and two-waycommunication with utility meter endpoint devices while at the same timeproviding an operating regime that conserves energy for long batterylife and utilizes the available airwaves for AMR communicationsefficiently. Embodiments of the invention are applicable in AMR systemsemploying handheld and/or vehicle-based mobile readers, fixed readers,and combinations thereof. Moreover, embodiments of the inventionfacilitate smooth transition from mobile AMR systems to fixed systems,and provide for automatic AMR system performance monitoring andautomatic adaptability to maintain or improve performance.

In an automatic meter reading (AMR) system 100 of the present invention,as depicted in FIG. 1, the components generally include a plurality ofutility or commodity consumption measuring devices including, but notlimited to, electric meters 102, gas meters 104 and water meters 106.Each of the meters may be either electrically or battery powered, orboth. AMR system 100 further includes a plurality of endpoints 108,wherein each corresponds to a meter. Endpoints 108 can be integratedinto their corresponding meters, or can be separate devicescommunicatively interfaced with their corresponding meters. Each of theendpoints 108 includes a radio receiver/transmitter such as, forexample, the Itron, Inc. ERT.

System 100 further includes one or more readers 109 that may be fixed ormobile. FIG. 1 depicts: (1) a mobile hand-held reader 110, such as thatused in the Itron Off-site meter reading system; (2) a mobilevehicle-equipped reader 112, such as that used in the Itron Mobile AMRsystem; (3) a fixed radio communication network 114, such as the ItronFixed Network AMR system that utilizes the additional components of cellcentral control units (CCUs) and network control nodes (NCNs); and (4) afixed micro-network system, such as the Itron MicroNetwork AMR systemthat utilizes both radio communication through concentrators andtelephone communications through PSTN. Of course, other types of readersmay be used without departing from the spirit or scope of the invention.

Further included in AMR system 100 is a system head-end, or hostprocessor 118. Host processor 118 incorporates software that manages thecollection of metering data and facilitates the transfer of that data toa utility or supplier billing system 120.

Automatic meter reading system 100 enables meter reading and two-waycommunications, including and command and control, between readers andendpoint devices, while maintaining backwards compatibility withexisting ERT-based AMR infrastructure. In the two-way communicationsregime of system 100, a number of advantages are achieved bysynchronizing reader 109 to endpoint 108, as opposed to the conventionalmethod of synchronizing the endpoint to the reader.

Conventional two-way meter reading systems synchronize by having eachendpoint listen for an initiation of communication by a reader, such asa reader-originated wakeup tone or command and control packet.Communication proceeds following the endpoint's reception of suchinitiating communication. In this type of arrangement, the endpointsmust be on, and operating in a listening mode, for communications to beinitiated. When an endpoint operates in a listening mode, butcommunications with the endpoint is not called for, the endpoint'soperation results in a waste of energy, shortening the life of theendpoint if the endpoint is battery-powered. If a reader attempts tocommunicate with an endpoint when the endpoint is not in its listeningmode, no such communication takes place, and the communication attemptresults in a needless channel utilization, which, in turn, prevents thereader from communicating at least on that channel during thecommunication attempt. Additionally, the failed communication attemptclutters the channel, potentially causing collisions or interferencewith other AMR communications.

AMR Communications Overview

FIG. 2 is a flow diagram illustrating an AMR system communicationsession 200 between endpoint 108 and reader 109 according to oneembodiment of the invention. In contrast to the conventional two-way AMRsystems described immediately above, endpoint 108 initiates eachcommunication session and, within the communication session, reader 109can selectively initiate two-way communications with endpoint 108. Inone embodiment of system 100, each of the endpoints 108 operates in alow-power standby, or sleep, mode for a majority of the time, asindicated at step 202. While in this mode, some endpoints 108 may gatherconsumption information from their corresponding utility meters. Reader109 normally operates in receive mode 204, in which it listens fortransmissions from endpoint devices. As indicated at process flow 205,reader 109 remains in receive mode in the absence of communicationsactivity.

In response to a specific event (such as, for example, the passage of acertain amount of time), endpoint 108 enters an active operating mode,or “bubbles up” and transmits an initial message, which is a relativelyshort message, such as burst of data, as indicated at step 206. Byvirtue of its short duration, the initial message requires a relativelysmall amount of energy to be transmitted by the endpoint. The initialmessage includes at least a unique identifier of the endpoint, and anynecessary overhead bits that identify the initial message as atransmission from an endpoint device to enable its reception by an AMRsystem receiver. In one example embodiment, the initial message includesa synchronization pattern (such as a string of alternating bits), apreamble that is recognizable by a reader as indicating the presence ofan AMR message, and an identification of the particular endpoint. Inanother embodiment, the initial message can include additionalinformation, such as, for example, consumption information.

In a related embodiment, the initial message is a 96-bit standardconsumption message (SCM) that is presently utilized in Itron Inc.'sERT-based AMR systems. An example of a SCM format is illustrated in FIG.3A. e.g., 21-bit preamble field followed by 2 ID bits, 1 spare bit, 2physical tamper bits, 4 endpoint type bits, 2 encoder tamper bits, 24consumption data bits, 24 ID bits, 16 CRC checksum bits (this can alsobe found in U.S. Pat. No. 4,799,059, which describes the ERT packet indetail). In related embodiments, the initial message is a variation ofthe SCM packet, such as having one or more additional fields, havingfewer fields, or having differently-defined fields. In embodiments wherethe initial message is shorter than a SCM (such as omitting anyconsumption information), further 2-way communication with the endpointsis needed to obtain the consumption information; however, greateroverall efficiency in communication and energy consumption may berealized with such an arrangement.

An AMR system in which endpoint devices wake from a standby mode totransmit a SCM is consistent with operation of present-day one-wayERT-based AMR systems. In this type of embodiment of system 100,endpoint 108 can work as a one-way endpoint with these existing systemswithout the need for upgrades or re-configuration of the readers andother AMR system infrastructure. Additionally, embodiments of readersaccording to the present invention can work conventional endpointdevices already deployed without any upgrades to the conventionalendpoint devices.

After transmitting the initial message, endpoint 108 may sleep in astandby state for some specified amount of time, as indicated at step208. In one example embodiment, the time of this delay is preset toabout 1 second. In other embodiments, there may be no such delay; or thedelay may be dynamically adjusted by the endpoint or configurationcommands via the AMR system. Following the delay of step 208, endpoint108 listens for a response from reader 109 for a predetermined durationof time, as indicated at step 210. Listening step 210 facilitatestwo-way communication between the endpoint and AMR system reader. Asdescribed below, if reader 109 is within communications range ofendpoint 108 and needs to communicate with endpoint 108 followingreception of the initial message, reader 109 transmits to endpoint 108during the endpoint's listen period. If no two-way communication isinitiated, communication does not take place and endpoint 108 returns toits bobble-up mode, as indicated at step 211. In an embodiment thatutilizes frequency hopping for communications with endpoints, the nextbubble-up event will involve the endpoint transmitting on a differentchannel.

In one embodiment, the listening duration is about 2 milliseconds. Invarious other embodiments, this listening time can be adjusted to anysuitable duration to facilitate the desired operation and performance ofsystem 100. In addition, the listening activity 210 of the endpoint cantake place at the same frequency, or channel, on which the initialmessage was transmitted, or can take place at a different frequency thatis predetermined, or formulaically derived based on specific conditions.

Prior to engaging in any two-way communications, at step 212, reader 109receives the initial message transmitted by endpoint 108 at step 206.Reader 109 then processes the initial message at step 214. In oneembodiment, processing the initial message includes decoding and parsingthe initial message, reading certain fields or information carried bythe initial message, and determining whether, and how, to respond toreceipt of the message. As indicated at decision 216, the response caninclude initiating a follow-up communication (i.e. in two-waycommunications mode). The decision for whether to initiate furthercommunication can be based on a variety of circumstances such as, forexample, the content of the initial message received in step 212, systemconfiguration instructions sent from the head end or host processor 118,the time of day or day of the billing cycle, the amount of time sincethe last successful consumption reading received from the particularendpoint 108, and the like.

At step 218, reader 109 transmits the follow-up communication as needed.In one embodiment, the follow-up communication is an instruction, suchas, for example, a command requesting certain additional informationfrom endpoint 108. In this scenario, according to one exampleembodiment, reader 109 reads the endpoint ID in step 214 when processingthe initial message and, based thereupon, reader 109 decides whether torequest the follow-up communication with that endpoint.

In a successful communication, step 218 occurs during the time thatendpoint 108 is in its receive mode according to step 210. In oneembodiment, reader 109 is synchronized with endpoint 108 (i.e.,configured to automatically account for the time delay of step 208) toensure that the follow-up communication transmitted in step 218 can bereceived. At step 220, endpoint 108 receives the follow-up communicationfrom reader 109. Endpoint 108 then processes the communication at step222, and initiates carrying out any instructions contained therein. Ifno further communication is called for, endpoint 108 returns to itsstandby mode of step 202. If the instructions received from reader 109require a communicative response, endpoint 108 may sleep for a specifiedtime duration at step 224, and then transmit the requested message atstep 226, to be received by reader 109 at step 228.

According to various embodiments, the requested message is to betransmitted by endpoint 108 at a specific channel or frequency that isknown by the reader. In one such example embodiment, the requestedmessage is transmitted at step 226 on the same channel as the originalinitial message of step 206. In another example embodiment, the channelfor transmitting the requested message is the same channel on which theinstruction was received at step 220. In other embodiments, thetransmission channel for the requested channel can be different.

The amount of information that is exchanged in the follow-upcommunication may be substantially greater than the amount ofinformation transmitted by endpoint 108 in the initial message. Forexample, reader 109 may request a large amount of consumption data orstatus information from endpoint 108. In response to this type ofrequest, endpoint 108 may transmit a 92-byte interval data message(IDM), a variable-length message packet on the order of 15-150 bytes, orcan include a much longer composite message distributed over a pluralityof separate packets. FIG. 3B illustrates a versatile message packetformat that supports message typing and variable length messaging. Theversatile message format depicted in FIG. 3B can accommodate a varietyof different messages including, but not limited to, consumption data(including interval data), status information, alerts and alarminformation, communications acknowledgements, information relating toendpoint or communications performance, and the like.

In one embodiment, the requested message can be implicitly requestedincident to command and control. For example, endpoint 108 can bepre-programmed to respond to certain received command and controlpackets with an acknowledgement-type communication. In this example, thepurpose of the command and control packet from the reader may not be toobtain data from the endpoint. Instead, the responsive communicationfrom the endpoint serves to verify that the command and controlinstruction was received correctly and carried out by the endpoint.

Following transmission by endpoint 108 of the requested message at step226, endpoint 108 sleeps for a delay period of step 208, and returns toits receive mode at step 210 to await any further instructions fromreader 109. In one embodiment, endpoint 108 is pre-programmed with aspecific default delay period for step 208. In a related embodiment, therequesting message from reader 109 sent at step 218 specifies aparticular delay period that overrides the default delay. Reader 109processes the received requested message at step 230, and determines ifany further two-way communications are needed at step 216. If anadditional instruction is to be sent to endpoint 108, the sequencedescribed above is continued beginning at step 218.

By synchronizing the reader to the endpoint in communication session200, the transmissions of the two-way communications are more likely tobe successfully received. The two-way communications can be coordinatedsuch that the receiver knows in advance at what time, and on whatfrequency, to listen for the endpoint's follow-up transmission.Additionally, the endpoint can be configured by the reader to listenduring a certain time, or to transmit during a certain time known by thereader. As a result, fewer communications attempts are needed to deliverthe messages having relatively large payloads (requiring more energy totransmit or receive). This permits operating the endpoint so that itspower consumption is minimized. Fewer communication attempts savesenergy, and results in a clearer channel, which reduces the chance ofcollisions with other data packets transmitted by other endpoints or AMRsystem devices. This, in turn, reduces the need for communicationsretries, keeping the channel clear and conserving energy at theendpoints.

Endpoint Side Communications Activity

FIG. 4 is a decision tree diagram illustrating examples of the responseof endpoint 108 to the initiation of two-way communications by reader109. At step 402, the instruction transmitted by reader 209 thatinitiates the two-way communications (such as the instructiontransmitted at step 218 in FIG. 2) is decoded. Three examples ofpossible instructions are illustrated: (a) the instruction may be arequest for the endpoint 108 to transmit certain data (and, optionally,that the transmission be carried out in a certain specified manner); (b)the instruction may be a configuration or programming command to adjustsome operating parameter of endpoint 108; or (c) the instruction may bea command to cause endpoint 108 to enter a specific mode of operationnotwithstanding (i.e., overriding) the endpoint's default operatingprogram.

In case (a) where the instruction is a request for data, endpoint 108responds at step 404 by transmitting the requested data as instructed.At step 406, endpoint 108 listens for further instructions for apredetermined time duration. If no further instructions are received,normal bubble-up operation is resumed as indicated at step 408. In case(b), endpoint 108 may receive configuration instructions to updateoperating parameters. Endpoint 108 responds by updating the operatingparameters at step 410 as instructed. At step 412, endpoint 108transmits a message to reader 109 confirming the successful updating,and enters into a listening mode at step 414 to await possible furtherinstructions. After the listening period, endpoint 108 returns to normalbubble-up operation at step 416. In case (c), endpoint 108 may receivean instruction to sleep for a specified duration of time. In response,at step 418, endpoint 108 enters a low-power sleep mode for thespecified time. The time duration may be specified in various ways, aswill be understood by persons of ordinary skill in the relevant art. Forexample, the sleep duration may be specified in terms of a real timeduration, or a time of day as measured, for example, by a real timeclock on board endpoint 108. Alternatively, the sleep duration may bespecified in terms of a count value to be traversed by a counter onboard endpoint 108 that runs while the endpoint is in its sleep mode.Following expiration of the time duration, endpoint 108 returns to itsnormal bubble-up operation as indicated at step 420.

In a related embodiments, reader 109 uses the follow-up communication toinstruct endpoint 108 to operate in a certain fashion, or to adjust oneor more configurable parameters of endpoint 108. For example, reader 109can command endpoint 108 to enter a low-power standby mode for a certaintime; or to preferentially utilize certain channels for futurecommunications. In another related embodiment, a request for a furthercommunication by reader 109 can include instructions on when, and how,to transmit the requested message in two-way mode. For example,referring again to FIG. 2, in step 218, reader 109 can specify theamount of time delay for step 224, and can specify the channel on whichto transmit the requested message at step 226. In embodiments whereinendpoint 108 and reader 109 are synchronized in time and in frequencyfor communications, the follow-on communications have an increasedprobability of being successful, thereby reducing the likelihood ofhaving to retry the communication. As will be discussed below, otheraspects of the invention provide further techniques for improving theprobability of successful communication.

Reader Side Communication Activity

FIG. 5 is a diagram illustrating reader 500, which is an exampleembodiment of reader 109. Reader 500 includes a radio circuit 502. Radiocircuit 502 is a half duplex or full duplex type radio that can transmitand receive. In one embodiment, radio circuit 502 can selectivelytransmit or receive signals using different modulation techniques. Forexample, radio circuit 502 can transmit and receive using amplitudemodulation (AM) techniques, such as on-off keying (OOK), as well asusing frequency modulation (FM) techniques, such as frequency shiftkeying (FSK), for example.

In one embodiment, radio circuit 502 is capable of receiving multiplechannels simultaneously. For example, radio circuit 502 can utilize abroadband front end section that amplifies substantially the entirecommunications band. The broadband front end feeds a digital signalprocessor (DSP) circuit that is programmed to discriminate betweenindividual channels using digital techniques. As will be appreciated bypersons skilled in the relevant arts, this DSP-based channelization maybe accomplished by a variety of known techniques. For example, the DSPmay utilize a plurality of digital filters tuned to each channel. Inanother example, the DSP may implement a Fourier transform algorithm,such as fast Fourier transform (FFT) to represent the communication bandin the frequency domain as a plurality of frequency bins, wherein eachchannel corresponds to at least one of the bins. The changing energycontent of each channel as a function of time is indicative of receivedsignaling on that channel. The receiver tracks the activity on eachchannel virtually simultaneously to detect the presence of, and recover,endpoint-originated transmissions. Radios of this type have beencommercialized in the AMR field by Itron Inc., of Spokane, Wash., USA.

Processor 504 is a controller circuit such as, for example, amicrocontroller, that coordinates the overall operation of reader 500.Processor 504 is interfaced with radio 502 via address/data bus or othersuitable communicative coupling. Processor 504 is also interfaced withprogram memory space 506, which stores the main operating instructionsof reader 500; configurable parameters memory space 508, which storesvarious adjustable settings; and with general memory space 510, whichcan store a variety of different data items during operation of radio500.

Database 512, also interfaced with controller 504, stores data relatedto the reading and configuration of endpoints that can communicate withreader 500. The endpoint data stored in database 512 can include a listof endpoints to which reader 500 is assigned, and endpoint-specificinformation corresponding to each of those endpoints. Examples of suchendpoint-specific information includes reading schedule(s) for when toobtain certain information from each individual endpoint, configurationand instruction information for adjusting operating parameters andestablishing certain operating modes at certain times, respectively, forselected endpoints; the time of, or since, the last successfulcommunication with each endpoint; received signal strength indication(RSSI) information corresponding to each endpoint; and the like.

When reader 500 receives an initial message from an endpoint, reader 500decodes the initial message to determine the transmitting endpoint'sunique ID. Reader 500 then looks in database 512 for a record matchingthe ID of the received initial message. If such a match is found, reader500 will track the time and channel at which the initial message wasreceived. This time and frequency tracking can include updating database512 or general memory 510 according to the tracked time and frequency.In a related embodiment, reader 500 tracks the time elapsed since thereceipt of the initial message. The elapsed time is used to synchronizea follow-up transmission to the endpoint's listen window during whichthe endpoint is receptive to instructions via two-way communications.For example, in the case where the endpoint sleeps for one secondfollowing transmission of its initial message and prior to activatingits receiver, reader 500 would respond with a follow-up communicationafter the passage of one second, as measured by a timer on board reader500.

During the passage of time following receipt of an initial message andbefore transmitting the follow-up communication, reader 500 continuesoperating its radio 502 to receive other transmissions from otherendpoints in its communication range. Each received communication istracked in time and frequency. In one embodiment, reader 500 implementsa message transmission schedule (e.g., in database 512, or in generalmemory 510). The message transmission schedule represents the times atwhich follow-up communications to each endpoint are to take place. Themessage transmission schedule can also include information indicatingwhich message to transmit to each corresponding endpoint. In one exampleembodiment, the message transmission schedule is implemented as a queuehaving time-stamped endpoint IDs. In another embodiment, the messagetransmission schedule is a queue of complete messages to be transmitted,each message corresponding to a time value. The time stamping or timevalue used to synchronize each follow-up communication with thereceiving endpoint's reception window can be referenced to the reader'sreal time clock, or to a counter value representing the delay timeduration between the reception of the initial message from thecorresponding endpoint and the planned time for transmission of thefollow-up communication to that endpoint.

In a related embodiment, the reader will not request a responsivemessage from an endpoint if the response channel has already beenallocated. The missed endpoint ID can be kept in a priority list and itwill have priority in the transmission schedule the next time an initialmessage is received from that endpoint.

In another embodiment, if the requested message was received by a readerfrom an endpoint, but the endpoint's message had errors, the readercould either wait until the next bubbled-up initial message or transmita second request in the two-way sequence after the previous request.This transmit request in the ongoing sequence can continue so long asthe applicable regulations governing channel use are complied with. Forexample, the “time on channel” rule set by the FCC limits the time of anendpoint/reader communication session to 400 ms in any 20-second timeperiod for each endpoint.

In one embodiment, reader 500 reserves time slots for receivingrequested messages from endpoints. Endpoints are instructed to scheduletheir requested message transmissions such that the transmissions occurduring a reserved time slot. Reader 500 disables its transmitter fromtransmitting in the communications band during the reserved time slots.In an example embodiment where all endpoint devices are configured tosleep for the same predefined time duration between the initial messagetransmission and the receiver operation, the reserved time slots forreceiving long messages occur periodically according to the predefinedtime duration. In one such embodiment, the delay time between initialmessage transmission and listen mode for endpoints is one second. Inthis case, the reserved time slots at receiver 500 can be at thebeginning of each 1-second block of time. The duration of each reservedtime slot can account for the length of time needed to transmit thelongest possible requested message, plus some buffer time to improvetolerance of timekeeping resolution errors between receiver 500 and anyof the endpoints.

In a related embodiment, for each block of time, a plurality of timeslots for receiving requested messages is reserved. Certain reservedtime slots may be assigned to requested messages to be received oncertain channels, while other reserved time slots may be assigned todifferent channels. As an example of this embodiment, for each periodicblock of time, a first reserved time slot may be assigned toeven-numbered channels, and a second reserved time slot may be assignedto odd-numbered channels. This arrangement ensures that requestedendpoint transmissions are not received simultaneously on adjacentchannels, thereby improving channel selectivity, improving the toleranceof receiver 500 to frequency drift of endpoint devices, reducing thelikelihood of inter-channel interference, and, ultimately, improving thelikelihood that the requested messages are received successfully. In avariation of this embodiment, there may be three separate reserved timeslots assigned respectively to every third consecutive channel.

FIG. 6 is a timing diagram illustrating two-way communications betweenreader 500 and a plurality of endpoints during four consecutive blocksof time I-IV. The arrows represent message transmissions between thereader and the endpoints; and the direction of each arrow indicates thedirection of transmission (whether from reader 500 to the endpoints, orvice-versa). In time block I, initial messages a b, c, and d aretransmitted by four respective endpoint devices. Messages correspondingto reference letters that are underlined in FIG. 6 correspond tomessages that are transmitted on even-numbered channels. For instance,initial messages a and d are on odd-numbered channels; whereas initialmessages b and c are on even channels.

In time block II, the reader responds with commands requesting messagesin the next interval. The responses directed individually to each of thefour endpoints are indicated at a′, b′, c′, and d′, respectively. Inthis example, every endpoint operates with the same time delay, onesecond, for example, between initial message transmission and listenmode. Therefore, each of the reader's responses a′, b′, c′, and d′, issent with the same time delay, e.g., one second, after the correspondinginitial message was received. Also, during time block II other endpointdevices transmit their respective initial messages e, f, g, and h. Thereader continues to monitor the communications band when it's nottransmitting and picks up initial messages e, f, g, and h.

In this example, there are two reserved time slots near the beginning ofeach time block for receiving requested messages. Each of responses a′,b′, c′, and d′ instruct the respective endpoint to transmit itsrequested message such that the requested message is received during theappropriate reserved time slot. Requested messages A and D aretransmitted on their respective even channels in the first reserved timeslot, requested messages B and C are transmitted on their respective oddchannels in the second reserved time slot. In a variation of thisembodiment, any of responses a′, b′, c′, or d′ can instruct therespective endpoint to transmit its requested message on a specifiedchannel or at a specified reserved (or unreserved) time slot.

In time block III, the reader responds to initial messages e, g, and h(not f) with commands e′, g′, and h′ requesting data. Also, the readerresponds to requested message B by requesting further data, as indicatedat b″. Additionally, during time block III, the reader receives initialmessages i, j, k, and l. Requested messages E, G, H are transmitted bytheir respective endpoints on even channels in the first reserved timeslot in time block IV. Requested message B is transmitted in the secondreserved time slot on its odd channel. If the reader requires additionaloperations from any endpoint, it will transmit the request according tothe endpoint's configured time delay following the previous readerrequest.

In another embodiment, the reader instructs multiple endpoints totransmit their requested messages at the same time, but on differentchannels, without having any of the channels reserved in advance. Inthis embodiment, the reader dynamically coordinates the channelassignments and scheduling in real time.

Two-Way Command and Control Functions

Table 1 below presents various examples of programming commands. Table 2presents various examples of data requests.

TABLE 1 Program Commands Set time/synchronize RTC Schedule AuditMode/GDT Mode Set Bubble-up rate Set TX power/Set TX Modulation Set timeduration for       Sleep       Pause after SCM before listen       Pauseafter download before TX       Pause after TX before listen Set defaultpacket type Channel utilization plan/Set default programming frequencySet encryption parameters Reset to factory setup

TABLE 2 Data Request Commands Specify intervals       Rows/columns      Evenly spaced in specified time range       Specify naturalduration and get last x intervals of       specified duration Movein/Move out info Gas day take info RSSI Encrypted messages Interrogateprogramming fields Battery voltage/Temp Tamper Report Query specificmemory location

These examples of two-way commands and data requests facilitate a numberof techniques for improving AMR system performance, such as endpointbattery life, probability of successful data communications, ease ofinstallation/upgradeability, migration from handheld mobile tovehicle-mounted mobile to fixed networks, obtaining a wide variety ofinterval consumption data from endpoint devices with minimalcommunications overhead, enabling special operating modes forfacilitating system audits and daily take measurements, and the like.

Adjusting Operating Mode for Endpoints

In one embodiment, readers can selectively place individual endpoints incertain operating modes. One example of such an instruction is the sleepcommand described above. In this mode, the endpoint sleeps for apreconfigured, instructed, or otherwise predetermined duration of time,then returns to its normal bubble-up operation. The sleep mode is usefulfor systems where further reads from the endpoint are not needed forsome time after a successful communication. This may be especiallyuseful in mobile readers. After collecting the needed data from eachendpoint, that endpoint can be instructed to sleep. When this command isapplied to every read endpoint, the result is a “trail of silence”behind the mobile reader. Endpoints that have been read no longer bubbleup, which clears the communication band of unneeded transmissions thatmight otherwise cause data collisions, necessitating re-tries andfurther cluttering the air waves. Since the likelihood of datacollisions is reduced, the sleep command can enable the use of longermessages for transferring more consumption intervals and otheradditional information. The time duration of the sleep mode can beconfigured to ensure that the reader is well out of communications rangeof the sleeping endpoint before it self-awakens by returning to itsnormal bubble-up mode.

In a fixed network embodiment, sleep mode may be employed to reduce thedensity of bubbling-up endpoints. For example, in a neighborhood havingendpoints A, B, C, D, E, and F, in close proximity to one another, thegroup of endpoints A, C, and E can be alternately operated in theirnormal bubble-up mode with respect to the group of B, D, and F. Thistechnique reduces the chance of message collisions. Another benefit ofthe sleep mode is that it conserves battery life for internally-poweredendpoint devices. For endpoint devices on a strict reading schedule, ifsupplementary reads are not needed between scheduled reads, the endpointmay be instructed to sleep until the next scheduled reading window.

Another example of a configurable temporary operating mode is a mode ofincreased endpoint activity. For example, in mobile network systems, autility provider may desire to conduct follow-up reads to collectadditional information from certain endpoints following a generalreading pass of a particular neighborhood. In such a system, endpointdevices may be configured to increase their bubble-up rate or theirtransmission power in a certain time window to increase the probabilitythat a possible follow-on read attempt will be successful. In situationswhere follow-on reads are likely to occur in a time window beginningafter a certain period, such as after several hours, and ending at theend of the next business day, the increased activity mode may bescheduled to begin and end to coincide with the time window. If readsare unlikely to take place in the time period after the last read andbefore the start of the time window for taking follow-on reads,endpoints may be commanded to sleep until the start of the increasedbubble-up activity. At the conclusion of the follow-on read window, theendpoints automatically return to their default bubble-up mode.

Another use of increased bubble-up activity is in facilitating day take,which is a reading taken by an endpoint at a specific time of day—forinstance, the consumption reading taken at 9:00 AM. Gas utilities oftenuse gas day take across a system to monitor daily usage of gas in theirsystem. Typical requirements are to read all of the GDT meters is asystem within a few seconds to a minute of the specified hour and thentake no longer than 1 hour to deliver the reading to the utility.

The two-way communications of the present invention enable programmingthe GDT time in the endpoint, and synchronizing the endpoint's real timeclock to the network or UTC time. In one embodiment, when the GDT timeoccurs in the endpoint a reading is taken and then stored in theendpoint. This GDT reading is then transmitted in a bubble up fashionfor 15 transmissions, at the standard bubble up rate the endpoint waspreviously running on, to permit multiple transmissions for good readreliability performance. Unlike usual bubble-up operation, which mayinvolve the endpoint transmitting a new measurement from one bubble-upevent to the next, the GDT mode in one embodiment repeatedly transmitsthe GDT value at every bubble-up event occurring while the endpoint isin GDT mode.

After the 15 transmissions, the endpoint will then return to its normalbubble-up mode. When the endpoint transmits the GDT to the fixed networkreader the GDT consumption is transmitted along with the current time ofthe endpoint given in the time since midnight. If the time is out ofspecification for getting GDT then the endpoint will be sent a new timefrom the fixed network reader.

A further example of operating mode adjustment that is afforded by thetwo-way communications aspect of the invention is adjusting operatingparameters to facilitate migrating the AMR system from one reader typeto another. Endpoints can be configured to bubble up slower in a fixednetwork installation than in a mobile system. Additionally, thetransmission power may be set higher in a fixed network when thebubble-up rate is slower.

Channel utilization is governed by different regulations throughout theworld. Each utility provider system can set and modify endpoint behaviorfor migrating their AMR systems to comply with the regulationsapplicable to it. In one example embodiment, the two-way communicationsare used to selectively reconfigure endpoint devices to operate underFCC Part 15.247 rules, or under 15.249 rules based on the desired levelof performance, the length of messages being transmitted, the measuredcommunication performance (e.g., RSSI) associated with communicationwith certain endpoints, the measured channel conditions (e.g., noisefloor or interfering signals), and the like.

In one example embodiment, endpoints may be programmed to bubble at aslow rate of one a minute until a monthly read time. Then, the endpointswould bubble up faster for a few days or until they are read. At thattime, the endpoints would be set to bubble slowly again. This approachkeeps endpoints available for unscheduled reads and, at the same time,conserves battery power and channel clarity.

Coordination of Communication Channels

As described above, the two-way exchange between reader and endpoint cantake place on the channel of the original initial message transmission,or can utilize different channels. In embodiments in which differentchannels are used for a particular two-way communication sequence, avariety of approaches may be utilized for coordinating the channelhopping. For example, the listening channel can be algorithmicallydetermined in some fashion, defined according to a specified channelhopping sequence known by both the endpoint and reader, or based on apredefined logical relationship to certain circumstances. This canprovide some degree of security from eavesdropping by an unauthorizedreceiver that does not know the hopping sequence. In a relatedembodiment, the listening channel can be derived based on the value of acertain data field of the most recently transmitted message (e.g., step206 or step 218 of FIG. 2) according to a known derivation algorithm.

In one example embodiment, the endpoint controls the channel hoppingsequence. For example, each transmission by the endpoint, such theinitial message or requested message, can include a field indicating thefrequency the endpoint's receiver will be listening to. In a relatedembodiment, each transmission (whether from an endpoint or from areader) will indicate the channel on which to transmit a responsivemessage. In another embodiment, the reader takes control of the channelselection when it initiates two-way communications. For example, thereader can specify the frequency on which the endpoint should transmiteach of its messages.

In embodiments where the reader controls channel selection, the readercan coordinate the activity of different endpoints to manage theutilization of the communication band. This degree of control can beused advantageously to avoid collisions. In one example embodiment, in amobile system, a reader uses two-way communications to transfer achannel hopping schedule to each endpoint. Each endpoint's channelhopping schedule can be unique to that endpoint, and can be designed tomake certain that endpoints that are located within a reader'scommunication range operate at different frequencies.

In one embodiment, the reader is adapted to detect whether the frequencyof the endpoint's transmission has drifted from the center frequency ofthe channel on which the endpoint is transmitting. For example, in asoftware-based radio such as the example embodiments described above,the receiver's radio can recognize if the energy of a received signal isappearing simultaneously in adjacent frequency bins. This suggests thatthe endpoint's transmission is not centered at the channel's frequency.In a subsequent message to the endpoint, the reader can include acommand to the endpoint to correct its channel definitions.

In another type of embodiment, other techniques of spectrum spreadingmay be utilized such as, for example, fast frequency hopping (i.e.,changing frequencies at a rate that is faster than the data rate), ordirect sequence spread spectrum (DSSS) techniques. Persons of ordinaryskill in the relevant art

Alarm/Error Handling and Call Back Conditions

In one embodiment, an endpoint can include certain alarm or error flagsin its initial message. The reader examines each initial message for thepresence of such flags and, if any alarm or error conditions arepresent, the reader can respond in some special manner. For example, thereader may request the endpoint to return the settings of certainconfiguration parameters, or may command the endpoint to return thecontents of a specific memory space and registers. As another example,the reader may treat certain error or alarm flags received fromendpoints as call back conditions under which to communicate thepresence of the alarm or error to the head end at the earliestopportunity.

If the endpoint 108 is on a meter, such as a gas meter, and all that isrequired are simple, once-a-day consumption reads, then the endpoint 108transmission packet may also confirm the data and may bubble less oftento conserve the battery. The packet can include a cyclical redundancycheck (CRC). Once the transmission packet is received by the reader 109,and if the reader 109 wants more information such as obtaining tamperdata, or to perform various functions such as resetting a register,setting timing, or adjusting frequency, the reader 109 is able to carryon a two-way interchange by transmitting the request when the givenendpoint 108 is listening.

Information Gathering and Decisions Based on Channel Conditions

According to one aspect of the invention, readers or endpoints measureand indicate the received signal strength (RSSI) for receivedtransmissions. In one such embodiment, a receiver measures the RSSI foreach received initial message. If the RSSI is below a certain predefinedthreshold, achieving a successful 2-way communication may be less likelythan desired, resulting in retries, waste of energy in battery-poweredendpoints, and channel clutter. The receiver can determine, based on theRSSI of a received initial message, whether to initiate two-waycommunications with that endpoint. By selectively communicating onlywith endpoints that appear to be communicating well, overall systemperformance can be improved, and wasteful failed transmissions can besubstantially reduced.

Conversely, if a first communication from a an endpoint is received witha particularly good RSSI (e.g., better than the average RSSI valueassociated with the endpoint), the reader can request more data than itnormally would. For example, the reader may request more interval datawith a higher granularity (e.g., 80 10-minute intervals as opposed to 4020-minute intervals). More generally, the extent of two-waycommunications may be dynamically selected by the reader based on theRSSI values of the transmissions from the endpoint.

In a mobile collection embodiment, a reader can compare an RSSI valueassociated with the most recently received initial message from acertain endpoint with that of the previous initial message from the sameendpoint. As the reader approaches the endpoint, the RSSI value isexpected to increase. Using this information, the reader may predict ifan endpoint's RSSI is likely to improve in soon-to-be-received initialmessages. The reader may thus elect to wait until a later time toinitiate two-way communications with that endpoint. In a relatedembodiment, the reader can identify a “best available” initial messagefrom an endpoint which is sending initial messages having lower thandesired RSSI values. For example, consider initial messages receivedfrom such an endpoint having the following RSSI values under the desiredminimum threshold of 0 dB: −12 dB, −6 dB, −3 dB, −4 dB. Based on thesevalues, future initial messages are not likely to be significantlybetter than the most recent value of −4 dB. Therefore, the endpoint mayelect to initiate the two-way communication with this endpoint followingreceipt of the next initial message from the endpoint.

In a related embodiment, the reader maintains records of past RSSImeasurements for each endpoint, or passes on the RSSI information to thehead end for maintenance of this information. Certain RSSI trends mayprompt the AMR system to adjust the way information is collected fromcertain endpoints. For example, in mobile systems, the route of themobile reader may be adjusted, or an endpoint may be re-assigned to adifferent data collection route or reader. In a fixed system, a repeatermay be placed to improve communications with certain endpoints incertain areas.

In one embodiment, fixed readers collect record of every endpoint thatis in range, together with the RSSI values associated with each of thoseendpoints, and provide this list to the head end. Certain endpoints maybe within communications range of more than one receiver. The head endcan determine which of these endpoints transmits to which reader withthe best RSSI, and, for each endpoint, instruct the best reader to addthat endpoint to its list of endpoint with which to initiate two-waycommunications. For readers that receive initial messages from certainendpoints at a lower RSSI than received by other readers at higher RSSI,these readers can be instructed to disregard initial messages from thoseendpoints. In a related embodiment, readers can communicate with oneanother to arbitrate which endpoints are to be associated with whichreceiver based on the RSSI values.

In one embodiment, if an endpoint's RSSI value is lower than desired,that endpoint may be instructed or programmed to increase itstransmission power for the two-way communication, or to bubble up morefrequently. In such cases, the utility provider may be advised by theAMR system to add additional battery capacity to the endpoint to supportthe higher levels of activity, thereby preserving the desired usefullife of the endpoint. In a related embodiment, if an endpoint's RSSIvalue is significantly higher than needed for reliable communications,that endpoint may be instructed to reduce its transmission power.

In another related embodiment, endpoints maintain records of RSSI valuesof received reader-originated transmissions. Readers may instructendpoints during the two-way communications to transfer their maintainedRSSI values. This information can be passed to the head end for systemperformance analysis. Certain decisions based on this information canalso be made by the readers. For example, in one embodiment, a readermay determine whether or not to transmit lengthy configurationinformation to an endpoint that is receiving a relatively weak readermessages.

Besides measuring RSSI values, readers or endpoints can measure channelclarity, and make certain decisions based on this information. In oneexample embodiment, a reader takes measurements of the noise floor ofdifferent channels during times of idle communications. In fixednetworks, such information may be used to characterize the communicationband as a function of time of day. If certain times of the day routinelyexhibit reduced channel clarity on certain channels, the reader mayadjust its operation to avoid communications on those channels. Thereader may disregard initial messages occurring on unclear channels, orthe reader may attempt to instruct endpoints using the two-waycommunications to preferentially utilize clearer channels. In mobilenetworks, readers may characterize channel clarity as a function of timeof day and of geographic location. Such information may be used toadjust the reader's operation similarly to the examples described above.In addition the reader's route may be adjusted to avoid certain deadspots, for example.

In a related embodiment, the reader measures channel clarity during thetime duration following receipt of an initial message from an endpointand the reader's communicative response thereto. If a channel is lessclear than a predetermined threshold, the endpoint may be instructed tochange channels, or to re-initiate communications at its next bubble-upevent on a different channel before requesting long messagetransmissions from the endpoint.

In another embodiment, the endpoints can measure channel clarity bylistening on the next channel prior to initiating communications with aninitial message transmission. If that channel is noisy, the endpoint maydecide to avoid transmitting its initial message on that frequency. Theendpoint may then switch to a new channel, and repeat the claritymeasurement prior to initiating communications. Endpoints may logmeasured channel clarity as a function of time, and pass thisinformation to the reader using the two-way communications when sorequested.

Repeaters

Referring again to FIG. 1, a repeater 122 may be used in the system 100and, if so, in one embodiment, the repeater 122 can function much likean endpoint. For example, repeater 122 may operate in a low-powerstandby, or sleep, mode for a majority of the time, and may bubble upwith an initial message directed to the main reader 109 similarly to theway an endpoint 108 operates. After the initial message transmitted byrepeater 122 is acquired by the main reader 109, reader 109 may instructrepeater 122 to transmit a list of endpoints within it communicationrange. The repeater follows this instruction by enabling its receiverfor some predetermined period of time, and logging the endpoint IDs ofendpoints transmitting initial messages that are received by repeater122.

Subsequently, repeater 122 bubbles up to initiate a communication withreader 109. Reader 109 initiates two-way communication with reader 122similarly to the procedure described above with reference to FIG. 2. Intwo-way communications mode, repeater 122 sends the IDs of the detectedendpoints to reader 109. Reader 109 determines which of these endpointsthe repeater 122 should track.

Repeater 122 may also monitor and record RSSI information similarly tothe techniques described above. The RSSI information can be used byeither the repeater, the reader, or the head end to instruct therepeater 122 and/or the reader 109 how to operate with respect to eachof the endpoints.

Reader 109 communicates a command to repeater 122 to instruct repeater122 to collect data from those endpoints. The repeater 122 thensynchronizes itself to those endpoints 108. When the reader 109 desiresa reading, it passes a command to the repeater 122 to collect reads. Therepeater 122 passes this command to the endpoints 108. Once all of thereads are collected, the repeater 122 passes them up to the reader 109.

In another configuration, the reader 109 passes an endpoint ID list anda reading schedule to the repeater 122. Repeater 122 communicates withthe endpoints on the list, and logs their consumption and related datain a database. When asked for end point reads, the repeater 122 sendsthe most recent readings from its database for each endpoint. Thismethod has the latency of the bubble time interval of the endpoint 108plus the reading cycle of the repeater 122.

In one type of embodiment, the repeater 122 is battery powered. Arepeater 122 of this type can sleep when it is not required to get datafrom the endpoints 108. Repeater 122 can wake at predetermined intervalsto bubble up to reader 109 and to listen for its endpoints 108. If ashort latency is required, the repeater 122 can operate a timer tosynchronize to the scheduled bubble-up times of endpoints 108. Iflatency is not an issue, the repeater 122 is able to turn on itsreceiver once an hour, for example, for a time duration long enough toread its endpoints 108, (e.g., 20 seconds for endpoints bubbling up morerapidly).

FIGS. 7A and 7B are process flow diagrams illustrating an exampleoperating sequence 700 involving a reader 109, a repeater 122, and anendpoint 108. Referring to FIG. 7A, repeater 122 operates in a low-powersleep mode until the next bubble up event, as indicated at step 702. Atstep 706, repeater 122 transmits an initial message that includes itsunique identification (from which reader 109 can determine that thetransmission is from a repeater, rather than from an endpoint). Reader109 operates at steps 204-205 212, 214, and 216 to receive and processthe repeater's initial message, and to determine whether to initiate2-way communications with repeater 122 as described above with referenceto FIG. 2. Repeater 122 and reader 109 observe the time delay of step708, during which time repeater 122 may operate in its sleep mode. Atstep 710, repeater 122 enters a receive mode, and at step 718, reader109 transmits an instruction to repeater 122, which is received at step720. If it is not received, repeater 122 returns to its default bubbleup mode of operation, as indicated at step 711. At step 722, repeaterbegins carrying out the instruction, after which the repeater may returnto its default operating mode, as indicated at step 723. If theinstruction included a request for information transmission, repeater122 observes time delay 724, after which it transmits the requestedmessage at step 726. Reader 109 receives the requested message fromrepeater 122 at step 728, and processes the same at step 730.

FIG. 7B illustrates an example sequence 750 that follows initiation ofinstruction processing step 722. Sequence 750 involves operatingrepeater 122 to communicate with an endpoint 108. In a practicalimplementation of this example, repeater 122 would likely communicatewith a plurality of endpoints 108 in the same manner. At step 754,repeater 122 enters into its receive mode to listen for any endpointinitial message transmissions. Unlike reader 109, which operates itsreceiver circuit most of the time, repeater 122 may remain in itsreceive mode for a limited time, as represented at step 755. Endpoint108 operates substantially as described above with reference to FIG. 2.

At step 762, the initial message from endpoint 108 is received byrepeater 122. The message is processed at step 764. This may includecomparing the endpoint's ID against the repeater's list of endpointswith which to communicate. Repeater 122 determines if furthercommunication is called for at step 766. Repeater 122 may forward theinformation contained in the endpoint's initial message and not requireadditional information from endpoint 108. In other situations, repeater122 may simply log the endpoint's ID as part of assessing the endpointsin its communication range. As described above, repeater 122 may requirefurther instructions from reader 109 to track this particular endpoint108. Assuming such communication is needed, repeater observes time delay208. Unlike reader 109, repeater 122 may sleep during time delay 208.Repeater 122 may also communicate with other endpoints 108 or with oneor more readers 109 during this time.

At step 768, repeater 122 transmits an instruction to endpoint 108. Theinstruction can initiate 2-way communications, configure endpoint 108,or command endpoint 108 to enter a specified operating mode, such assleep mode, for example. Repeater 122 then observes time delay 224,during which it may sleep or communicate with other endpoints orreaders. Repeater 122 enables its receive mode 754 in time to receive,at step 778, the endpoint's requested message transmitted at step 226.At step 780, repeater 122 processes the requested message. In oneexample embodiment, the processing step 780 includes parsing and placingthe information of interest contained in the received requested messagefrom endpoint 108 into a queue or into a composite message fortransmission to reader 109.

The performance of the repeater 122 does not have to equal that the mainreader 109 in terms of receiver sensitivity and transmit power. Rather,the repeater 122 can be used primarily as a hole filler or AMR systemrange extender. Repeaters can also be utilized to improve AMR systemcommunication traffic management. For example, repeaters can be assignedto groups of endpoints, and their communication times can be scheduledto utilize the airwaves efficiently and avoid collisions from excessivetransmissions.

A significant benefit of the repeater is that it is low cost, easy toplace, and provides desirable battery operation. Battery operationpermits functionality during power outages, and substantially reducesthe cost of installing the repeater. Additionally, battery operationfacilitates placement of the repeater in locations where mains or otherexternal sources of power (e.g., sunlight) are unavailable. In oneembodiment, a repeater has the same hardware platform as an endpoint.For battery-powered repeaters, additional or larger batteries than thosepresent in typical endpoint devices may be installed to facilitatelonger life between service calls.

Interval Data Longing

According to another aspect of the invention, an endpoint stores a largequantity of consumption measurements in its memory. This storage spacecan store many more intervals than can be transmitted in a typicalinterval message packet. For example, in one embodiment, the endpointstores 40 days of hourly consumption data. The intervals associated withthis data are can be tracked by a real time clock (RTC) of the endpoint.The RTC can be synchronized periodically by the readers using thetwo-way communications protocol described above.

In one embodiment, as depicted in FIG. 8A, the interval data is storedin a data structure that is an array with 40 rows (days) and 24 columns(hours). In another embodiment, as illustrated in FIG. 8B, the array canhave three or more dimensions. Referring to the example of FIG. 8B, thearray arranges interval reads taken every minute, together with hourlydata, and daily data. The column indicated at 852 represents dailyreads, taken on the second hour and at the third minute. The column orrow indicated at 854 contains minute-by-minute reads taken on day 5,hour 2. The column or row indicated at 856 contains hourly reads on day2, taken at minute 2.

More generally, this aspect of the invention structures the consumptiondata in tiers of time granularity. At the finest granularity, every itemof meter data is present. For example, if consumption readings areobtained every 10 seconds instead of hourly, the finest level ofgranularity would be 10 seconds. At the next tier of time granularity,only one or more subsets of the full set of meter data is included. Forexample, if readings are taken every minute, and if the utility providerwishes to obtain hourly reads and weekly reads, then hours and weeks canbe included as separate dimensions in the data structure.

Each cell in the array can contain the total (absolute) consumptionmeasured when the value was stored in that cell, or can contain a deltavalue relative to an adjacent cell or to a reference value.

When the endpoint is operating, it will sequence through each cell ofthe finest time granularity, then the next finest, and so on, filling inthe consumption or delta value in the corresponding cell. This processcontinues to the last row of the array. When the array is full, thecells can be populated starting at the opposite coordinate (i.e., itwill wrap around and start over)

Since the endpoint has knowledge of time, it can be configured to alwayssample its finest granularity interval data at the same instant. Forexample, in the case of hourly reads, the endpoint can store theinterval information as it existed at the top of each hour.

Referring to the example of FIG. 8A, when a reader requests a set ofdaily reads, such as for move-in/move-out, the endpoint will return themost recently completed column from the array. This will return an arrayholding the consumption values for the last interval and 39 deltas forthe previous days.

A dump of the entire interval array is possible as a series of commandsunder FCC Part 15.249 rules. To conduct a “Dump All” a programmer isutilized, and the programmer will accomplish this task at 0 dBm on theprogramming frequency. The programmer can perform a series of 24Interval requests to get the 24 sets of hourly interval readings thatconstitutes a dump of all intervals.

By structuring the collected data at the endpoint in this manner,requests by the reader or repeater for certain intervals to be returnedby the endpoint can be communicated simply. For example, a request forinterval data can specify which row or column (or plane, etc.) isdesired. Additionally, in situations where large amounts of intervaldata are being transferred, and an error is detected, a follow-upcommunication by a reader can request specific intervals that were lostin the failed portion of the earlier communication without having tore-transmit the entire set of interval data.

In a related embodiment, a reader can utilize two-way communications tore-configure the time granularity definitions in the endpoint. Inanother related embodiment, an endpoint may be configured to transmitinterval data at a different data rate. For example, in a mobile systemwhere a reader is in communications range with each endpoint for alimited amount of time, the data rate for larger interval data messagesmay be set to a higher value to enable more data to be communicatedduring the available window.

Example Implementation

The following describes a specific implementation of the RF Based MeterReading System described in the paragraphs immediately above. In thisembodiment, communication occurs in the 900 MHz ISM band. It couldhowever be implemented at different frequencies without departing fromthe spirit or scope of the invention. On off keying (OOK) and frequencyshift keying (FSK) modulation are utilized.

Initially, an endpoint, such as endpoint 108 (FIG. 1) bubbles up totransmit a SCM. Immediately after transmitting an SCM the endpoint 108goes into receive mode. The SCM that is transmitted is sent using OOK orFSK. OOK can be used for backwards compatibility with existing readers,and for power savings (since approximately ½ of the bits require zeroenergy to transmit). FSK can provide improved performance.

When the endpoint 108 goes into receive mode it utilizes an FSKreceiver. The SCM is modified by appending the channel that the receiverwill listen on. In addition, other information may be appended such astamper flags requesting an immediate call back from the reader 109. Whenthe reader 109 receives the SCM, if it requires more information fromthe endpoint 108, it will carry on a two-way FM session with the module.The SCM will bubble up from the endpoint 108 on fixed intervals. It willalso be transmitting at 1 mW (i.e., 0 dBm) to be compatible with theexisting endpoints 108 already deployed and operating under FCC 15.249rules. Since the SCM synchronizes the endpoint 108 to the reader 109,any two-way FM transmissions that follow can utilize higher powertransmissions and operate under FCC 15.247 rules. If the SCM istransmitted at a controlled frequency, with little drift, then thereceiver trying to read it can be a narrow band receiver. By using anarrow band receiver, the receiver sensitivity can by increased by over5 dB, over existing reading devices that employ wideband receivers ofaround 250 kHz. These endpoints would be backward compatible intoexisting ERT-based AMR systems.

In one embodiment, advanced readers 109 employ a DSP radio enabling thereceive bandwidth to be set by DSP firmware. This arrangement enablesreading previously-existing legacy endpoints 108 with reducedsensitivity. The system at this level can be used primarily by a mobilemeter reading system that utilizes readers such as handheld readers andvehicle-mounted readers. The bubble rate is set to maximize battery lifeand to provide the desired level of system performance. Since it is atwo-way system, the reader 109 is able to tell the endpoint 108 tobubble at a much slower rate until the next read time. This savesbattery life but still leaves the endpoint 108 available for reads.

As the deployment is migrated from a mobile meter reading system to afixed network meter reading system, the endpoints 108 can be programmedto transmit the data at a much slower rate. In an example of a fixednetwork situation, only the ID is transmitted to reduce transmissiontime. If the data rate is reduced to 1200 baud about 10 dB of gain canbe realized. Since the transmission time will be longer, the bubble ratecan be reduced to maintain battery life. A system running in this modeis able to use fewer readers that are placed in the field. The two-wayFM link can still be used; however, higher transmission power may beneeded to match the AM performance in either mode (fast or slow datarate). If a channelized receiver is used it is possible to transmit theSCM at a higher power, e.g., +10 dBm, and comply with FCC 15.247 ruleson the AM bubble up.

Further development of this system includes having the endpoint 108operate under 15.247 rules FM two-way all the time. This system would bemost appropriate for electrical meters that are line-powered. Theelectrical meters can transmit as often as they want and leave theirreceivers on to keep synchronization with a fixed network radio.

In order to get better coverage over a deployed metering system, arepeater 122 can be implemented. This repeater 122 is used mainly as ahole filler. The repeater 122 is not intended to have the same receiversensitivity and, as a result, it can use lower cost and lower powercomponents. It is possible to have the repeater 122 run off of lithiumbatteries at relatively low cost. The repeater 122 can bubble up justlike an endpoint. Once it is acquired by the reader 109, it is told togo into a listen mode to find all of the endpoints 108 in its area. Therepeater 122 then transmits the IDs of the endpoints 108 within itscommunication to the reader. The reader 109 compares the list to theendpoints 108 that the reader 109 can communicate with. The reader 109then instructs the repeater 122 to listen only to the endpoints 108 thatthe reader 109 cannot communicate with reliably. The repeater 122 tracksthe endpoints 108 by turning on its receiver at the time the endpoint108 is due to bubble up.

In the case of monthly reads, the repeater 122 can stay asleep for mostof the month and then turn on and acquire its endpoints 108 near thereading time. In general, if the reader 109 wants a reading from anendpoint 108 under a repeater 122, the reader 109 tells the repeater 122on the two-way FM link. This happens after the repeater 122 bubbles upits ID. The repeater 122 then waits for the endpoint 108 to bubble upand either uses the SCM data or requests additional data. Once the datais obtained the repeater 122 sends it up to the reader 109. It may besent as soon as it is acquired or it may synchronize with the nextbubble up. To minimize the number of channels the repeater 122 or reader109 look for the endpoint 108 on, a select number of channels can beused for bubbling up. These channels can be distributed across the ISMband. This arrangement works under the FCC .sctn.15.249 rules.

Quantitative Improvement

The quantitative improvement provided by the specific implementationdescribed above can be better understood when described in contrast tothe Itron meter reading technology of today. The Itron meter readingtechnology of today operates under FCC 15.249 rules. The endpoint 108transmits at 1 mW (i.e., 0 dBm) output power and its receiver has asensitivity of around −90 dBm. This receiver operates in the MAS band,which requires an FCC license. The readers 109 for this system generallyfall into two categories: (1) A mobile reader such as a van that has areceiver sensitivity of −113 dBm and a wake-up transmitter output powerof around +38 dBm; and (2) Other Readers, e.g., handhelds and fixednetworks, having a receiver sensitivity of around −108 dBM and a wake-uptransmitter power of +23 dBm and +30 dBm, respectively. The RF link intoday's encoder/receiver/transmitter (ERT) system is:

-   -   Van to ERT=123 dB Reader to ERT=108 dB    -   ERT to Van=113 ERT to Reader=108 dB

Aspects of the present invention, at a first level, address a mobilemeter reading system. Specifically, this aspect provides backwardcompatibility and provides for future migration. Embodiments of thepresent invention operate to limit the amount of frequency drift fromthe endpoint 108 so that a receiver with a narrower bandwidth can beused. Using a frequency locked RF chip such as the Bluechip BCC918 andconfiguring it to transmit OOK at low power provides a frequency stableendpoint. This then enables the use of a narrowband receiver andincreases receiver sensitivity. If the bandwidth is reduced from 256 kHzto 50 kHz then around a 7 dB sensitivity improvement can be realized.The frequency stable endpoint 108 can bubble up an SCM transmission,thereby removing the need for a wake-up transmitter. This transmissioncan have, for example, an output of 0 dBm that is compliant with FCC.sctn.15.249 rules just like the Itron ERT of today. If the endpoint 108is deployed in an existing system, an existing reader 109 can read itwith the same performance as the existing system. If it is in a newdeployment then a new reader can read it with a 7 dB improvement in thelink. The new reader 109 can read existing ERTs as well. If a DSPchannelized receiver is employed then the receiver can decode on anarrow channel for new endpoints 108 or it can average channels togetherto get the required bandwidth to read old endpoints 108. When readingold endpoints 108 the system performance is that of an old system, i.e.,7 dB less link than a new one. The RF link in the system of according tothis embodiment (for mobile systems) is:

-   -   ERT to reader=116 dBM (based on new CCU4 receiver sensitivity of        −109 dBm)

The SCM that is transmitted can include information appended to the endof the message. This does not interfere with the ability of an oldreader to decode the message and it does provide additional informationfor the mobile meter reading system. Additional information can includea channel number for the reader 109 to call back on as well as priorityflags that may indicate a power failure, for instance, requiring animmediate callback from the reader 109. After the endpoint 108 sends theSCM packet, it either listens on the same channel on which ittransmitted the SCM, or notifies the reader of the channel number onwhich that it will be listening as part of the SCM packet, for example.The endpoint 108 then goes into receive mode and listens on that channelfor a short period of time, e.g., 5 to 10 milliseconds. The receipt ofthe SCM synchronizes the reader 109 to the endpoint 108 (in time and infrequency) so the reader 109 knows when and where to locate the endpoint108. If the reader 109 requires more information such as ID or responseto a power fail it can initiate two-way communications on the channelthat the endpoint 108 will be listening on as described above.

The two-way communications between the reader and the endpoint arefrequency modulated (e.g., FSK) and at a higher power. Since both endsare synchronized the two-way communications can take place under the FCC15.247 rules. Using the example of a bluechip RF part, the endpoint 108has a receiver sensitivity of −105 dBm at 9600 baud (19.2 k Manchesterencoded). The receiver's transmit power is +10 dBm. If the reader 109has a transmit power of +10 dBm and a receiver sensitivity of −105 dBmthen it would match the performance of the AM SCM link. The RF FMtwo-way link in the system of this embodiment (for mobile systems) is:

-   -   ERT to reader=115 dB    -   Reader to ERT=115 dB

One example of a SCM message format is as depicted below:

Preamble ID and Data CRC (optional) Next Channel (optional

At a second level, embodiments of the present invention are applicableto fixed meter reading networks. When the AMR system is sufficientlysaturated with endpoints that the utility provider wants to move to afixed network solution, the endpoints already deployed in the mobilesystem can be reconfigured to operate in a somewhat different regime. Inone example, the system remains a bubble up system but it bubbles up ata slower rate. The data rate is also reduced to 1200 or 2400 baud. Inthis mode, the endpoint 108 can bubble up only its ID to reduce transmittime. Alternatively, the endpoint can transmit an SCM or SCM-likepacket.

At the slower data rate, a processing gain of about 10 dB can berealized at the receiver. This gives the receiver an effectivesensitivity of about −126 dBm. A slower data rate can be used for thetwo-way exchange as well, improving the receiver sensitivity. Since thisis a fixed network, the endpoints are always in range of the reader, sothere is no time window in which communication must be completed. Byutilizing a quality low noise amplifier (LNA) that is commerciallyavailable in the reader's receiver, and cutting the data rate in half, a5 dB gain in reader sensitivity on the FM link can be obtained. Thisprovides a sensitivity of −110 dBm in the FM receiver.

The endpoint receiver gains around 3 dB in sensitivity from a slowerdata rate. The reader 109 can transmit at 18 dBm on the FM link. If aBluechip ASIC is used, a power amplifier can be included to increase itsoutput from 10 dBm to 16 dBm. This gives a balanced link for both the AMbubble up and the FM two-way links. The fixed network RF links of thepresent invention are as follows:

-   -   AM Endpoint to reader=126 dB    -   FM endpoint to reader=126 dB    -   FM reader to endpoint=126 dB

Repeaters

The issue of holes in the reading area of a fixed network is of realconcern. As such, a repeater 122 can be used to relay information froman endpoint 108 to the reader 109. The repeater 122 does not have thesame performance as the main reader 109 because it is mounted closer tothe endpoint 108 and is much lower in cost than the reader 109. Further,the repeater 122 can be battery-powered so that connecting to the mainsis not a concern. The repeater 122 can use an RSSI type decoder fordecoding AM signals from an endpoint 108 and has a sensitivity of −106dBm. In one embodiment, the repeater 122 bubbles up its ID just like anendpoint.

When a reader 109 acquires the repeater 122, the reader 109 instructsthe repeater to enter a listen mode to find all of the endpoints 108within communication range. This leaves the repeater 122 receiver on formany tens of seconds while it locates the IDs of endpoints 108 bubblingup in its vicinity. The repeater 122 then sends this information up tothe reader 109. The reader 109 will determine which of the endpoints 108it cannot communicate with and instruct the repeater 122 to listen toonly those endpoints. In an alternative embodiment, this selection mayhappen further up the chain at the head end to arbitrate between systemcells and determine which repeater 122 will be assigned which endpoint.When it is time to read the endpoints 108, the reader instructs therepeater 122 to get a reading when the repeater 122 bubbles up its ID.The repeater 122 then collects the reading from the endpoints 108 andpasses them up to the reader 109. This may cause latency in the system.

One example technique to reduce this latency is for the reader 109 totransmit a reading schedule to repeater 122. This enables repeater 122to perform the reading of its assigned endpoints 108 automatically.Repeater can send its collected endpoint data to the reader 109 duringthe next bubble up period. To conserve power, the repeater 122synchronizes its receiver time to the anticipated transmit time ofendpoints 108 in its domain; the repeater 122 sleeps 2 Q between reads.For the endpoints 108 and the repeaters 122, if the reading schedule isregular, e.g., daily reads, then the endpoints 108 are instructed tobubble up at a slower rate for 23 out of 24 hours. The endpoints 108 andrepeaters 109 then increase their bubble rate as the read time getsnear. Once the reading is obtained the endpoints 108 and repeater 122bubble slowly again. While bubbling up at a slower rate permitsunscheduled reads to take place, it may take longer to get them.

Battery Life

The following description provides an analysis of estimated battery lifethat may be attainable in endpoints operating according to aspects ofthe invention. In this embodiment, an endpoint uses a 3.6 V lithium ionA cell battery having a capacity of approximately 3.3 A-H.

The average current from the battery during transmission is about 96.5mA in 24 dBm mode, or about 22 mA in 10 dBm mode. The duration of theSCM transmission is 5.86 ms. This would give 347.4 mW in 24 dBm mode and79.2 mW in 10 dBm mode. Multiplying these values by 5.86 ms produces 2mW-seconds for 24 dBm and 464.1 uW-seconds in 10 dBm.

The processor draws slightly less than 2 micro amps when the endpoint isin its sleep state. The receiver circuit draws about 15.2 mA for 2 msduring the listening time windows, or 109.6 uW-seconds.

All of these values averaged over the bubble up period work out to anaverage current draw of about 14 uA, which can be sustained for 20 yearson the A cell. This estimate includes taking into account empiricallyobserved non-linearities in the battery drain based on load conditions.

IDM messages, or requested messages having longer packets can havevariable length. A typical IDM response is expected to be about 120 bitsat 16384 bits/sec, or 7.3 mS. In this embodiment, IDM messages are sentat about 24 dBm, or 347.4 mW. IDM transmissions occur only when asked,which is generally on the order of once per month, so they represent anegligible impact to the overall battery life. when endpoints areoperated as such.

Extending Transmission Duration

Conventionally, the transmitter circuit includes a power regulator thatmust receive a supply voltage in excess of a certain threshold. Onechallenge with long transmissions is their high power draw can load thesupply, causing a dip in supply voltage, thereby shutting down the powerregulator. While conventional approaches to mitigate this effect, suchas placing capacitors across the power supply, are well known, theseapproaches provide only limited advantage due to size and costconstraints associated with using large capacitors.

FIG. 9 is a circuit diagram illustrating an example embodiment of aswitched capacitor arrangement for temporarily boosting the availablepower for powering the transmitter circuit during data transmissions.This voltage boost permits the power regulator to operate above itsthreshold voltage for a longer time, thereby enabling longertransmissions. In normal low power mode switches SW1 and SW2 are closedand SW3 is open. These switches may be implemented with transistors,transmission gates, relays, or the like. In this configuration theoutput voltage is 3.6 volts. With the capacitors C1 and C2 connected ina parallel configuration the current drawn from the module is shared byboth capacitors. The parallel bulk capacitance is sufficient foroperating an endpoint and producing short high powered transmissions.When a high voltage level is required, such as for transmitting longerhigh powered data messages, switches SW1 and SW2 open and SW3 closes.This provides 7.2 volts at the output. This higher voltage can be usedto provide improved overhead for the transmitter. Advantageously,because the capacitors are already charged there is no charging latencyto produce the higher voltage virtually immediately. When the high powermode is no longer needed the capacitors are switched back to a parallelconfiguration. The capacitors are then recharged in parallel. There islatency in recharging the capacitors but it is much smaller than thebubble up times required by the AMR.

Resistor R1 is shown to represent the series resistance of the battery.Additionally, R1 could be used to limit the charge current of thecapacitors, minimizing the current drain and therefore voltage sag onthe battery. Capacitors C1 and C2 are sized so that when they areconnected in series they provide enough capacitance for the high poweredmessage transmission.

Low Cost Mobile Daily Interval Meter Reading System

The mobile daily interval reading system according to embodiments of thepresent invention utilizes the concepts described above but furtherexpands on the earlier discussion by applying additional techniques forcollecting daily interval data.

The mobile daily interval reading system works as described hereinbelow. If an endpoint 108 is deigned to transmit at a higher power,e.g., +10 dBm, and the receiver has a sensitivity of −114 dBm, aone-mile range can be achieved in a mobile environment. If the endpoint108 is a bubble-up endpoint 108 that transmits every ten seconds and thereader 109 travels at 30 miles per hour the reader 109 is in range forapproximately 100 seconds. The endpoint 108 can be configured totransmit either in AM or FM and send an initial message such as theStandard Consumption Message (SCM) that the Itron ERTs send today. Itcan also have an FM receiver with a sensitivity of around −109 dBm forlow data rate messages. After the endpoint 108 transmits its consumptiondata it listens on the same channel it transmitted on. If this is usedin an electric meter the endpoint 108 can leave its receiver on as longas it is not transmitting.

As described above, this system can be modified to improve field servicelife in battery-powered products. When the reader 109 receives a messagefrom the endpoint 108 it can take a measurement of the signal strength(RSSI) and determine if the endpoint 108 is in range or the channel isclear enough for subsequent transmissions. If the RSSI value is below athreshold, or if the channel is not clear the reader 109 does not replyand the endpoint 108 retransmits its SCM ten seconds later on anotherchannel as part of its normal bubble-up operation.

When the RSSI is strong enough and the channel appears to be clear, thereader 109 transmits a command to the endpoint 108 to send some numberof intervals and on what channel or channels. The reader 109 transmitsthis request at +10 dBm, or could go to +20 dBM if needed. This complieswith the 15.247 rules because the endpoint receiver would be trackingthe transmitter of the reader 109. Actually, the transmitter of thereader 109 is tracking the endpoint receiver since the reply is on thesame channel that the endpoint transmitted on. It is possible for theendpoint to skip a pre-defined number of channels up or down from itslast transmission just to keep the band randomized, but this is notrequired.

The endpoint 108 can send data to the reader 109 at a higher data ratethan the SCM transmission, e.g., 20k bits per second. If the endpoint108 is in an electric meter it can save 15 minute interval data in 2bytes (16 bits) of memory. There are 96, 15 minute intervals in a 24hour period. If the endpoint 108 transmits 35 days worth of intervals,that amounts to 3360 intervals, or 53,7690 bits. Allowing for someoverhead, that number can be rounded to 60,000 bits. At 20,000 bits perseconds (BPS) the endpoint 108 can transmit 35 days of 15 minuteinterval data in 3 seconds. If the data rate is increased to 32,768 BPSthe transmission time is 1.83 seconds for 35 days worth of data. A datarate of 32,768 BPS should cost about 3 dB in receiver sensitivity.However, with 110 seconds in range and only 1.83 seconds to send thedata there is some sensitivity, and therefore range, to give up. The FCCrules for 15.247 specify that at the higher power a transmission canonly last 0.4 seconds in a 10 second period on any one channel. Theendpoint 108 can hop between channels to send all of the data. To send35 days worth of data the endpoint 108 would hop over 5 to 6 channelsdepending on packet overhead. If a transmission is lost due to a hop toa noisy channel the endpoint 108 can be instructed to resend only thatblock on another channel.

Once all of the data is transmitted the endpoint 108 is instructed toreset any registers that need to be reset and then told to go to sleepfor a specified period of time, e.g., 10 minutes, to keep the band clearof unneeded bubble-up transmissions. A system such as this can utilize alimited number of commands to the endpoint 108 to keep the systemsimple. The commands can include:

-   -   Send X number of past intervals    -   Send block X on channel X    -   Reset registers, the endpoint may reply with an ACK    -   Send time of use (TOU) data    -   Sleep for X time

Additional commands may be added without departing from the spirit orscope of the invention.

This system approach is possible because of the more than 16 MHz ofbandwidth available in the ISM band. A alternative of the present systemis to have the reader 109 tabulate all of the endpoints 108 that bubblein a 5 second interval. The endpoints 108 would leave their receivers onlong enough to wait for the response. The reader 109 would then requestdata, from all of the endpoints 108 with which it communicated, onfrequencies spread through the ISM band. This approach is desirablebecause when the reader is transmitting it cannot receive. Using a DSPbased multichannel receiver multiple transmissions can be receivedsimultaneously. Not only can interval packets be received but themultichannel receiver can continue to listen for new candidates bubblingup. It can also read and decode legacy ERTs during this time

By collecting 15 minute interval data for 35 days, a utility is allowednot only to do monthly reads but to obtain profiling data fordistribution optimization as well. Move in, move out could be billed tothe nearest 15 minute interval. The reading performance of this systemis similar to, or better than, that of the mobile collector. It allowsbasic SCM type reads or higher functionality reads from the sameinstalled base. If the reader does not want the additional data it doesnot request it.

The present invention may be embodied in other specific forms withoutdeparting from the spirit of the essential attributes thereof;therefore, the illustrated embodiments should be considered in allrespects as illustrative and not restrictive, reference being made tothe appended claims rather than to the foregoing description to indicatethe scope of the invention.

1-157. (canceled)
 158. A method in a reader used in an automatic meterreading (AMR) system, the method comprising: receiving a one-waycommunication from an endpoint; initiating a two-way communication withthe endpoint in response to receiving the one-way communication; andduring the two-way communication, sending an instruction to theendpoint, the instruction configured to adjust a bubble-up operationparameter in the endpoint.
 159. The method of claim 158, wherein thebubble-up operation parameter includes at least one of: scheduling aperiod of increased bubble-up activity of the endpoint during the twoway communication, putting the endpoint in a sleep mode for a specifiedtime duration, and slowing a default bubble-up rate.
 160. The method ofclaim 159, wherein slowing the default bubble-up rate further includesat least one of: increasing transmission power level, and responding toa specified reading time by temporarily increasing a bubble-up rate.161. A method in a reader used in an automatic meter reading (AMR)system, the method comprising: receiving a message from an endpoint at aparticular frequency; determining whether the particular frequency issuitably centered within a predefined communication channel associatedwith the message; initiating two-way communication with the endpoint;and during the two-way communication, sending an instruction to theendpoint, the instruction specifying a frequency correction for theendpoint to implement.
 162. A method in a reader used in an automaticmeter reading (AMR) system for assessing communication reliability, themethod comprising measuring channel clarity; and making a decisionaffecting future communication with at least one endpoint based on themeasured channel clarity.